msg_socket: impl for Arc and Mutex

These types are simple wrappers, and so this change just adds trivial
passthroughs.

For data sent over a socket, the data is not Arc-ed or Mutex-ed on the
other end with the same ref count or lock. Sending over the data is more
like a deep copy, rather than a simple ref count increase.

TEST=cargo test -p msg_socket
BUG=None

Change-Id: I519096b0b3b6ab75e79c37addf0d60ce3da4a717
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2168586
Commit-Queue: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
diff --git a/Cargo.lock b/Cargo.lock
index e9da7f9..41843ee 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -447,6 +447,7 @@
  "futures 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.44 (registry+https://github.com/rust-lang/crates.io-index)",
  "msg_on_socket_derive 0.1.0",
+ "sync 0.1.0",
  "sys_util 0.1.0",
 ]